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JavaScript JavaScript and the DOM (Retiring) Traversing the DOM Sibling Traversal

Julien Arseneau
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Julien Arseneau
Full Stack JavaScript Techdegree Student 5,200 Points

Can someone explain to me how to highlight an element?

The elements won't highlight.

app.js
const list = document.getElementsByTagName('ul')[0];

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {
    let li = e.target.parentNode
    let  ul = li.parentNode
    ul.insertBefore.highlight
  }
});
index.html
<!DOCTYPE html>
<html>
    <head>
        <title>JavaScript and the DOM</title>
    </head>
    <link rel="stylesheet" href="style.css" />
    <body>
        <section>
            <h1>Making a Webpage Interactive</h1>
            <p>Things to Learn</p>
            <ul>
                <li><p>Element Selection</p><button>Highlight</button></li>
                <li><p>Events</p><button>Highlight</button></li>
                <li><p>Event Listening</p><button>Highlight</button></li>
                <li><p>DOM Traversal</p><button>Highlight</button></li>
            </ul>
        </section>
        <script src="app.js"></script>
    </body>
</html>

2 Answers

For this challenge you need to add a class to an element using DOM traversal. The 'highlighting' is not really relevant.

Since we're not adding new nodes, we don't need the insertBefore method.

We need to know which button was clicked (e.target), then we use previousElementSibling to find whatever element is immediately before it (the p tag we need), then we access the list of classes it contains, then add the class of highlight to that class list.

const list = document.getElementsByTagName('ul')[0];

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {

    e.target.previousElementSibling.classList.add('highlight');

  }
});